The study will measure sedimentary denitrification rates at selected sites in the Chukchi-Beaufort continental shelf regions of the Artic Ocean as part of the Shelf Basin Initiative (SBI). Overall denitrification by facultative anaerobic bacteria in this region is a function of several factors including the oxygenation state of underlying sediments, spatial and temporal variation in organic matter inputs, bottom water nitrate concentrations, and the rates of sedimentary bioturbation and bioirrigation as well as water column processes. Denitrification along the wide Artic shelves is currently estimated to be a significant portion of the global oceanic denitrification rate and additionally responsible for consuming a significant fraction of the pan-Artic inorganic nitrogen budget. Denitrification in this region will likely be subject to the impact of global climate change brought about by either altered circulation patterns, such as changing inflow patterns of high nutrient Pacific waters through the Bering Straits, or climate driven changes in ecosystem structure and function resulting from altered sea-ice distributions. In order to better understand the present variability of nitrogen cycling in this Arctic shelf basin, the investigators will extend a limited number of denitrification rate measurements previously made in the region, and relate these to one or more of a number of contributing environmental drivers.